Introduction: The force with which two bodies in our universe attract one another, say the Earth and the Moon, is found by using an equation based on Newton's Universal Law of Gravitation, a law that states that the force with which two bodies attract one another is directly proportional to the product of their individual masses and inversely proportional to the square of the distance between the bodies. The equation that summarizes Newton's Law of Universal Gravitation is shown below:

[math]F_g={Gm_1m_2}/r^2[/math], where [math]F_g[/math]=gravitational force, m=mass, G=the universal gravitation constant, and r=distance between the centers of the two bodies under consideration

Based on Newton's Universal Law of Gravitation, as the masses of bodies increase, the gravitational force of attraction also increases. On the other hand, as the distance between the centers of the two bodies increases, the gravitational force of attraction decreases. This helps to explain why there may not be as much attraction between two given bodies in the solar system if they are further away from one another, as opposed to being very close to one another. It is important to note that the SI unit for gravitational force is the Newton (N), as it is for forces in general.